Air is always pushed into any engine, either by atmosheric pressure or by a higher pressure in boosted case. There is no such thing as pulling air. In a boosted engine the air coming in will have more velocity since the pressure is higher, I guess that is what you mean. Corky Bell says quench is most important. He says you can change other things but never mess with quench. Hemi type heads like on the Northstar engine don't have quench areas. So who knows. I'll follow what Corky Bell says for now.

 

well if you want to get technical about it there is not pushing or pulling it is just pressures trying to equalize themselves, its either vacumme being created by piston movement causing a pull or the atmosphereic pressure trying to occupy more space in a push.


But anyways I've been thinking about this. What makes this quench area so special? Is it because it's on the outside of the burn, or is it because its in a sliver of a space? What would happen if we theoretically dropped the piston 0.5" into the hole? There would be no quench, but if the piston isn't comming that close to the head what makes it different than the rest of the combustion chamber???

 

Since I questioned the original need for quench, at least I can explain how it "can" help the combustion process.

First, a smaller chamber will complete the burn faster since there is less distance for the flame to travel across the chamber. Since the burn is completed faster, there is less "time" for detonation. This is where a smaller chamber (more quench) has higher detonation resistance.

Second, quench is the area that fuel is not "able" to burn in the cylinder.
But... the cylinder is fired before TDC anyway. Therefore the flame front starts across the whole bore & is then constricted to the chamber area as the piston approaches TDC. This turbulence supposedly helps the burn efficiency as well.

Small chambers will allow higher compression for a given octane. My motorcycle will run on 87 octane w/ 11:1 compression & still make 150hp/liter.
It has a small bore, but oddly enough no quench area.

New combustion chamber designs now offer more piston surface area (less quench) than old engine designs. Look at the old SBC fuelie style heads with a deep small chamber. These offer more quench than the new larger diameter shallow heart shaped styles that are the norm. Why are the new chambers not worse for detonation as they offer less quench? We now routinely run 11:1 on premium pump fuel & this will not work on older motors with early style heads.

Also, most multi-valve motors have no room for quench. Look at the new Cobra motors.... large shallow chambers. I've seen these do 20# boost on pump fuel.

I have one of these in the garage now.... I did cover it so my Camaro doesn't have to look at it......

Seems as though chamber shape & quality of combuation may have more effect than the quench...... just a thought.

Just thought I would keep the thought process fresh. If no one thought outside the accepted boundries we would still be running carbureted flatheads.